Engine oil, which is supplied to the sliding portions that require lubrications, is stored in a crankcase of the engine. An air-cooled engine is used in an all-terrain vehicle (so-called as “ATV”). In the air-cooled engine, the engine is cooled by only the wind so that the temperature of the engine oil tends to rise.
To solve this problem, Japanese Patent Laid-Open No. 2002-225574 discloses an air-cooled engine having an oil cooler assembled to the engine body so as to cool the engine oil.
Furthermore, Japanese Patent Laid-Open No. 9-296991 discloses the air-cooled engine having an oil cooler to which an oil filter is directly assembled.
In order to improve the radiation performance of the oil cooler, it is desirable that enough winds blow the oil cooler. However, in the case that the oil filter is directly assembled to the oil cooler, the oil filter prevents the wind from blowing the oil cooler, as a result the cooling performance is not improved.
On the other hand, the oil cooler can be placed at a portion appropriate for cooling by connecting the oil filter and the oil cooler with a pipe. In this structure, however, pipes and connectors are required to assemble the oil cooler and the oil filter to the engine body. For this reason, the oil cooling system will be complicated. This causes not only increasing the assembling time of the engine but also increasing the production cost.